A technique is known in which an operation rate of a compressor is increased more than that during the non-execution of a deceleration lock-up immediately after the execution of the deceleration lock-up is started, an increase of the operation rate of the compressor is finished upon the elapse of a predetermined time Tup after the start of the execution of the deceleration lock-up and the operation rate of the compressor is reduced more than that during the non-execution of the deceleration lock-up immediately after this end of the increase (JP 4399989B).